The Smoke Pit : Stripping an 80's 2-stroke carb

Stripping a very gunged-up Mikuni carburettor, off a neglected 133cc Yahamaha RZR 2-stroke. Despite its sorry state, its a welcome relief from the concurrent issues with the "snakepit" 1986 Aisan on my Daihatsu car, because its comparatively SIMPLE.

One thing's bothering me though. I want to put the needle to soak in carb cleaner, but I can't get the rubber/plastic (?) depth stop (?) off, and I don't really want to expose it to carb cleaner long term.

I also can't offhand see how its supposed to work. There are rings on the top of the needle that a little C-washer locates in. I THINK they are supposed to provide an adjustable depth stop for tuning, BUT in fact the depth seems to be fixed by the rubber/plastic thing, which won't move, so it looks like they only affect the spring loading on the needle.